1. Technical Field
The invention relates generally to systems for converting fluid-dynamic energy, such as from air and water, into mechanical energy. In particular, the invention relates to an open or closed field turbine in a wind tunnel, or hydrodynamic tunnel, for converting kinetic and potential energy into mechanical/electrical energy in an open eolian or hydrodynamic plant.
Furthermore, the invention relates to a closed system where the conversion of energy occurs in an environment where pressure is regulated and maintained above the atmospheric, level.
2. Background Art
Eolian and hydrodynamic energy offers many advantages. It is widespread all over the country and does not cause pollution. Compared with other kinds of alternative energies, such as solar or geothermal energy, it is easily available as mechanical energy and consequently can be converted into electric energy.
Unfortunately, present conventional wing-blade aerogenerators have a limited power coefficient and produce relatively unstable work with respect to time. Efficient use of wind energy is considerably limited by low energetic concentration with average annual values of power per surface unit stroked by the blade reduced to the minimum. Efficiency is also impacted by daily and annual irregularities and variables.
Eolian plants are over-dimensioned with respect to the power generated because of the aforementioned problems and also because of the low energetic density that is obtained from wind. Eolian plants also must have great mechanical strength to tolerate strong winds.
Wind energy is essentially the kinetic energy of the mass of air in motion due to barometric or thermobaric atmospheric events. Therefore, the power effective available is proportional to the cubic wind speed, but it is also in a direct relation with the potential energy of the air mass due to the earth""s gravity force (10000 kg/m2xe2x80x9410 meters water column).
Dependence of power density on cubic wind speed sets forth the considerable influence that local ventilation characteristics have on technical and economic performances of an aerogenerator according to the prior art and makes the conversion of energy more complex. If the wind speed doubles, as it often happens for short periods, it is possible to obtain eight times the power and it is necessary to provide for a control system to skim the wind, reducing the blades stroke surface or lowering the efficiency of the rotor to avoid overloads. On the contrary if the speed reduces itself to one half, the converted power reduces itself substantially to an eighth, making it impossible to rely on the designed nominal power of the eolian plant.
Many kinds of rotors are known from the prior art, but the more tested recently have been rotors with a horizontal axis (parallel to the wind direction) that have fixed blades with a single blade, double blade, triblade, multiblade and cycloblade hub. Recently, the single blade system with a variable pitch terminal part of the rotor is being used in larger plants.
Conversion systems with a suitably shaped Magnus effect rotor that rotates with respect to the blade-holder hub, both central or peripheric, are not employed.
Patent RM 94 A 000529 owned by SILE/FLUID-SERVICE relates to a method for amplifying the dynamic surface pressure in mechanical machines where the dynamic surface pressure related to the fluid dynamic action of any gaseous or liquid composition is directed towards the external or lateral surfaces of an oppositely rotating thrust cylinder pair thus producing downstream of the cylinders themselves dynamic thrusts, which are greater than those obtained by means of a corresponding flat and static two-dimensional surface subjected to the same fluid dynamic thrust action.
Patent RM 94 A 000813 also owned by SILE/FLUID-SERVICE relates to a system for converting kinetic and potential energy in an eolian plant that channels fluid vein gathered by a concentrator into a central body where it interacts with the thrust rotors with an optimal incidence angle and where the reaction section with the rotors may be dimensionally regulated.
Furthermore, it is known that pressurization, a static method for filling a closed container with predetermined pressure according to the plant model, allows energetic density. This activates the kinetic component of the energy incident on a rotating element, to be increased when pressure and density are increased. Therefore, it is possible to work with low fluid speed and consequently low rotors speed even if working conditions are characterized by the same power and the same efficiency. In fluid-dynamics this may be related to the situation wherein, in a fall hydraulic system, the static head is a basic factor to define the dam power since flow rate is a fixed value that does not change with time. Therefore, if the hydrostatic basin supplies a limited power with the same section of fall tube, a greater fall pressure could be obtained by raising the basin.
Experimental work on Magnus effects started at the beginning of this century, and has been disclosed in a number of scientific international papers.
GB-A-2 031 072 discloses a wind energy exploitation system wherein the body of the blade does not rotate around its own axis but is hinged to a vertical shaft whose rotation movement generates electric energy. The blades lift when the wind speed increases in order to allow to take advantage also of weak winds.
In document GB-A-2 179 014, instead, the Magnus effect is exploited. This document uses this effect for the position control of a ship or for its propulsion, but not for generating energy.
U.S. Pat. No. 4,366,386 relates to a chiral turbine with xe2x80x9cbladesxe2x80x9d which are perfectly cylindrical, and the turbine is placed in a non-pressurized environment.
Another example of the Magnus effect is the rotating cylinder used to power the Flettner and Cousteau rotor ship. Although cylindrical xe2x80x9cbladesxe2x80x9d or xe2x80x9crotorsxe2x80x9d may be the best solution in the case of the Flettner and Cousteau rotor ship, they cannot be applied with practical and advantageous results in the case of a relative rotation between the xe2x80x9crotorxe2x80x9d and the direction of the fluid in motion. This means, in particular, that the yield for the most common wind speeds over the course of the year (weak winds) would be low.
It should be noted that these solutions relate to an applicative method of the xe2x80x9ctranslationxe2x80x9d type, which involves a lift force distribution in KNm, in a parallel form, on the whole surface of the rotating cylinder.
According to the dynamical point of view, both in the eolian and hydrodynamic environment, a geometric configuration is not suited for a rotating blade that must also rotate on a rotation axis with different corresponding peripheral velocities that increase from the root of the xe2x80x9cpropellerxe2x80x9d towards the terminal region of the blade, where the peripheral velocity has the largest value.
Consequently, a cylindrical configuration from the root to the end of the turbine (or propeller) is not adequate for the dynamical exploitation of all velocities related to the Magnus effect.
The mathematical computation, the numerical simulation, and the already realized turbines, have demonstrated that, in order to obtain a dynamically correct form, the geometric configuration of the rotating rotor (blade) must assume a particular geometric shape, that is a xe2x80x9cbulbxe2x80x9d shape, on the distal end of the rotating blade itself.
The inventor generally refers to an inventive rotor having a bulb-shaped geometry as a xe2x80x9cchiral rotorxe2x80x9d or a xe2x80x9cchiral turbine.xe2x80x9d The meaning of the word xe2x80x9cchiralxe2x80x9d is an opposite dynamic action (180xc2x0) as will appear from the description (see for instance FIG. 4).
The inventive chiral turbine is a new machine which is suited to exploit the dynamical components and the potential of any fluid substance in motion at slow velocity. Examples of these fluid substances include free air (wind), free water (rivers with low hydrostatic pressure and with a low speed of the water stream in m/s), gaseous composition (air or nitrogen in pressurized circuits).
Under the engineering point of view it is recommended to use the following definitions:
chiral turbine: complete machine including the blade units
chiral rotor: single blade unit
bulb, or chiral bulb: peripheral body of the blade.
An object of the present invention is to provide a method and a turbine operating in a closed or open (free air-river stream) cycle system to convert kinetic and potential energy in an eolian environment, and more generally in a fluid-dynamic environment, wherein the rotating blades interacting with fluid vein are provided with their own rotation motion around their more extended axis. This make is possible to exploit pressure amplifying effects resulting from the Magnus effect, in a particular blade shape.
Another object of the present invention is to provide a method for converting energy associated with fluid-dynamic actions in a pressurized environment, which allows lower involved work speeds, by means of machines based on the application of the Magnus effect principle, at the same time maintaining high efficiency and a high conversion rate of kinetic and potential energy in electromechanical energy.
Still another object of the present invention is to provide a method for converting energy associated with fluid-dynamic actions in a pressurized environment, that permits reduction of the dimensions of plants and machines where the conversion of energy associated with the fluid-dynamic action is performed.
A last object of the present invention is to provide a method and a chiral turbine with an open or closed system in a wind tunnel for converting eolian kinetic and potential energy, in a pressurized environment and more generally in a fluid-dynamic and hydrodynamic ambit. Although this invention implies a new conception according to the basic principles of the same invention, it applies known technologies and constituent materials making the invention easier to carry out.
These and other objects, which will appear from the description below, are attained by means of a system where rotating blades constituting the interaction means with the fluid in motion, are shaped as lengthened structure with a bulb-shape end and are constituted as chiral rotors that are able to rotate on their own more extended axis according to the Magnus effect principles, besides in the radial direction according to fluid advance direction.
Such bulb shape allows the best exploitation of rototranslation speed components of the rotating blade and of the incident kinetics. It is for this reason that blades under a fluid-dynamic action are equivalent to an accelerated mass, which is placed in the zone of an energetic and potential differential, caused by the spin rotation. Therefore, the accelerated mass of the chiral rotor is subjected to the attraction resulting from a pressure jump, which produces aerodynamic lifts and falls.
Hence, the rotation of chiral blades cause a condition of kinetic and energetic differential asymmetry in the space where the pressure potential is reduced. As this occurs just in the proximity of the translating mass (chiral rotor), the same is subjected to the induced pressure differential, defining aerodynamic lifts and falls.
A temporary relative energetic unbalance, to restore the symmetry with respect to pressure variation, produces a feedback which makes the mass (chiral rotor) subject to the potential differential that has been established between the two bodies: chiral rotorxe2x80x94fluid. This produces a considerable thrust pressure on the chiral rotor.
According to another aspect of this invention, a method in which a fluid is introduced in an environment, closed by means of a containment vessel, where pressurization is obtained by means of compressors arranged in complementary structures is shown. Said closed environment is subdivided into a first fluid vein delivery section comprising a sequence of bipolar rotors and into a second fluid vein return section, which lies inside the first section, and comprises a second sequence of bipolar chiral rotors.
Fluid is directed in such a direction to collide with the first sequence of bipolar chiral rotors. Each one rotates around its own axis and is arranged coupled in a multistage sequence 180xc2x0 out of phase one respect to the other, in the couple arrangement, wherein the containment vessel shape is such that at the end of the first multistage sequence of chiral rotor couples, air flows are conveyed in the return direction, in a couple of return conveyors where the aforesaid second sequence of chiral rotors are arranged, allowing the optimal exploitation of the fluid vein and of the present static potential to be reached, through their serial arrangement.